Oracle sid case sensitive

The following is what I encountered during the test. I did not have it before, but it seems that I can use lower case letters. But today, when I change the archive location, I can only use upper case sid.

In my environment, Oracle sid is case sensitive, as follows:

Alter system set log_archive_dest_1 = 'location =/oracle/racw.arch 'scope = spfile sid = 'racdb1 ';
Alter system set log_archive_dest_1 = 'location =/oracle/rac2_arch 'scope = spfile sid = 'racdb2 ';
The setting is successful.

Alter system set log_archive_dest_1 = 'location =/oracle/racw.arch 'scope = spfile sid = 'racdb1 ';
Alter system set log_archive_dest_1 = 'location =/oracle/rac2_arch 'scope = spfile sid = 'racdb2 ';
The setting does not take effect, or the original configuration.